ESPs are assembled on a rig floor and the overall length of the assembly varies with the application. There is a direct relationship between the required output pressure and the length of the assembly. In the past these pumps have been used in shallow wells where the overall length was within the limits of surface equipment to suspend and still allow access to the bottom of the finished assembly that was accessible at or above the rig floor. More recently the applications have been in deeper wells requiring additional stages for the ESP and getting the overall length of the ESP assembly to the order of 100 meters or more. The surface equipment cannot suspend assemblies that are this long outside the wellhead.
In some applications the ESP is assembled on a parallel orientation to the tubular string going into the well using a Y-connection assembly. This assembly allows the ESP to be positioned parallel to the string so that tools can go straight through the string while the ESP is in essence on a sidetrack. The preferred way to mount the ESP is to use the upper Y-connection to suspend the weight of the ESP. When this is done there is room for thermal expansion when downhole without putting any compressive stresses on the ESP housing. In shorter assemblies the way this is done is that there is a Y-connector uphole and a pup joint below the pump with an extending pedestal aligned with the flange connection on the upper Y-connector. The pump is built up on the extending pedestal that has an available axial adjustment. The pump is normally fully assembled in the derrick on the bottom support and then the height of a telescoping joint near the Y-connection is adjusted so that the mating flange on the Y-connector comes down to the discharge flange of the ESP. After the flanged connection is bolted up at the top of the ESP, and the telescoping joint is locked, the adjuster at the bottom, which is still accessible on the rig floor, is backed off to allow the ESP to be suspended by its housing from its discharge flange that is bolted to the Y-connector. In this manner the housing has room to grow due to thermal loading once lowered into the borehole.
The problem arises when the length of the ESP is such that its lower end that rests on the extending pedestal is already in the hole when the upper end of the pump is assembled. While the Y-connector can be brought down to allow bolting up the discharge flange of the ESP there is no longer any access to the lower end of the ESP to remove the lower support as was done before with shorter assemblies that left the lower end accessible on the rig floor. Because of the tight fit of the parallel ESP and main string in the wellbore and the fact that the ESP and the adjoining tubular are secured to each other with fasteners as the ESP is assembled, there is no longer a way to raise the ESP far enough to get its weight to hang off the discharge flange.
The present invention addresses this issue by eliminating the need to raise the ESP when its lower end is on a pedestal in the wellbore while still putting the ESP in a condition where its weight hangs off the discharge flange to allow room for thermal expansion. Instead the pedestal comprises an interventionless removable support so that the ESP can be assembled as before with the shorter versions and then run in the hole at which point the support already in the hole would be undermined shifting the hanging weight of the ESP to the Y-connector. In the preferred embodiment the temporary support is a controlled electrolytic material as described in US Publication 2011/0136707 and related applications filed the same day. These and other aspects of the present invention will become more readily apparent from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.